Multicylinder internal combustion engine with externally supplied ignition

ABSTRACT

This disclosure is directed to a multicylinder internal combustion engine with externally supplied ignition, which has a fuel vaporizing device which is connected to individual intake tubes of the engine via a line system. The line system is embodied as branching in such a way that only respective combustion chambers which are not operated in direct ignition sequence (1-3-4-2) are connected in pairs to each other and jointly via a central line to the fuel vaporizing device. The multicylinder internal combustion engine with externally supplied ignition, is provided for motor vehicles.

PRIOR ART

The invention is based on a multicylinder internal combustion enginewith externally supplied ignition. The patent application GB 2 248 087has already disclosed an internal combustion engine that has an intaketube that transitions into an intake manifold from which individualintake tubes branch to the individual combustion chambers or to theindividual cylinders of the engine. By means of fuel injection valvesdisposed in the individual intake tubes, upstream of inlet valves of thecombustion chambers, fuel can be delivered into the individual intaketubes in order to prepare an ignitable fuel-air mixture, which flowsinto the combustion chambers when the inlet valves are open. Anelectronic engine control device controls the fuel quantity delivered bythe fuel injection valves as a function of the aspirated air mass of theengine and as a function of other engine operation parameters.

In addition to the injection by means of the individual fuel injectionvalves, the engine has another injection valve that is part of a centralfuel vaporizing device which can prepare fuel vapor which is thendelivered into the intake tube upstream of a throttle mechanism that isembodied, for example, in the form of a throttle valve. The delivery offuel vapor by means of the fuel vaporizing device is limited to thelower load range, in particular to the idling range of the engine. Inthe upper load range, particularly in the full load, though, only thefuel injection valves associated with the combustion chambers or thecylinders deliver the required fuel. The delivery of vaporous fuel intothe intake tube is intended to prevent, to the greatest extent possible,a re-condensation of the fuel vapor against cold walls of the enginethat would otherwise occur during the starting phase of the engine inorder to thus be able to sharply reduce the emission of pollutingexhaust components, in particular hydrocarbons.

It is, however, problematic that depending on the ignition sequence ofthe individual cylinders or their intake sequence, because of areciprocal influence of the cylinders during intake of the fuel vaporprepared by the fuel vaporizing device, due to intake tube oscillations,this fuel vapor is only distributed unevenly to the individualcombustion chambers of the cylinders. However, this results in anincrease in the emissions of polluting exhaust components so that it isnot possible to maintain extremely low exhaust values as well as asmooth running of the engine.

ADVANTAGES OF THE INVENTION

The engine according to the invention has the advantage over the priorart that a virtually uniform distribution of the fuel vapor or afuel-air mixture prepared by the fuel vaporizing device to theindividual combustion chambers of the engine can be achieved so that itis possible to maintain extremely low exhaust values as well as a smoothrunning of the engine.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the invention are shown in simplified form inthe drawings and are explained in detail in the description below.

FIG. 1 is a sectional representation of a partial view of an internalcombustion engine according to the invention,

FIG. 2 shows a first exemplary embodiment according to the invention ofa line system for the engine,

FIG. 3 shows a second exemplary embodiment according to the invention ofa line system for the engine.

DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

In a sectional representation, FIG. 1 shows a partial view of aninternal combustion engine 10, which has four cylinders 1, 2, 3, 4 orfour combustion chambers 13, wherein in FIG. 1, only a single cylinder 1with one combustion chamber 13 is depicted. Each combustion chamber 13has at least one inlet valve 14 and one spark plug 19. Upstream of theinlet valve 14, at least one fuel injection valve 12 is provided on anindividual intake tube 15 of the engine 10, which can deliver fuel intothe individual intake tube 15 in the direction of the inlet valve 14.The four individual intake tubes 15 lead, for example, from an intakemanifold 16 that is part of a continuing intake tube 17 of the engine10. A throttle mechanism 18, which is for controlling the air quantityaspirated by the engine 10 and is accommodated in the intake tube 17, isembodied, for example, in the form of a throttle valve and isaccommodated so that it can rotate in the intake tube 17. The airaspirated from the surroundings by the engine 10 flows via an airfilter, not shown in detail, in the direction of an arrow 20 drawn inFIG. 1 and into the intake tube 17, where it flows further into theintake manifold 16 when the throttle valve 18 is open and is thendistributed by this intake manifold via the individual intake tubes 15to the individual combustion chambers 13 of the engine 10.

Upstream of the throttle valve 18, an idling air line 24 branches offfrom the intake tube 17 and leads to a mixing chamber 25 of a fuelvaporizing device 26. A throttle 32 can be disposed in the idling line24, for example in the form of an orifice, which limits the air quantityflowing in the idling line 24 by means of throttling. The fuelvaporizing device 26 has, for example, a central injection valve 27 thatis equipped with a heating attachment 28. The heating attachment 28comprises a vaporizer structure 29 that can, for example, beelectrically heated in a known manner, for liquid fuel and for thispurpose, has resistance heating elements 31, which can, for example,have a positive temperature coefficient (PTC) or a negative temperaturecoefficient (NTC). For example, an electronic control device, not shownin detail, can be provided to control the resistance heating elements31. The resistance heating elements 31 are accommodated in a vaporizerhousing 30 and are embodied, for example, as plate-shaped and if needbe, have a porous surface. A central line 35 leads from the mixingchamber 25 of the fuel vaporizing device 26 and transitions into abranched line system 36, which produces a flow connection of theindividual combustion chambers 13 of the engine 10 to the mixing chamber25. The line system 36 is embodied as branching according to theinvention into the individual intake tubes 15 of the engine 10 in such away that only respective combustion chambers 13 or cylinders 1, 2, 3, 4which are not disposed in direct ignition sequence in relation to oneanother, are connected in pairs to each other and jointly via thecentral line 35 to the fuel vaporizing device 26 or the mixing chamber25.

The line system 36 according to the invention for a four-cylinderinternal combustion engine with externally supplied ignition is shown inmore detail in FIGS. 1 and 2. The engine 10, indicated in FIG. 2 bymeans of dashed lines, has four cylinders 1, 2, 3, and 4, which,diverging from the depiction in FIG. 2, are in reality disposed oneafter the other in the sequence 1, 2, 3, and 4 and are operated with anignition sequence, for example, of 1-3-4-2. The central line 35 leadingaway from the fuel vaporizing device 26 branches into a first cylinderpair line 38 and a second cylinder pair line 39. The first cylinder pairline 38 branches further into a first cylinder line 41 for the firstcylinder 1 and a second cylinder line 42 for the fourth cylinder 4. Inthe same way, the second cylinder pair line 39 branches into a thirdcylinder line 43 for the third cylinder 3 and a fourth cylinder line 44for the second cylinder 2. The resulting branching points of the lines35, 38, 39, and 38, 41, 42, and 39, 43, 44 have a Y-shape with legs,which preferably enclose an angle that is as acute as possible betweenthe branching lines 41 and 42; 43 and 44 in order, by means of anincreased flow resistance, to thus minimize a reciprocal influence ofthe cylinders that are connected to each other in pairs. For the sake ofcompleteness, it should be mentioned that it is also possible to embodythe branching points in a T-shape. Since the first cylinder line 41 isconnected to the first cylinder 1, the second cylinder line 42 isconnected to the fourth cylinder 4, the third cylinder line 43 isconnected to the third cylinder 3, and the fourth cylinder line 44 isconnected to the second cylinder 2, the provided ignition sequence ofcylinders 1-3-4-2, i.e. ignition by spark plugs 19 first of cylinder 1,then cylinder 3, then cylinder 4, and finally cylinder 2 results in thefact that only respective combustion chambers or cylinders that are notoperated in direct ignition sequence are connected to each other inpairs and are connected to the fuel vaporizing device 26 via thecylinder pair lines 38, 39 and the central line 35.

The lines 35, 38, 39, 41 to 44 of the line system 36 are preferablyembodied in the form of tubes or hoses that are comprised of an elasticmaterial with a low heat conductivity, e.g. plastic. The connection ofthe cylinder lines 41 to 44 or the introduction of fuel vapor into theindividual intake tubes 15 occurs in relative proximity to the inletvalves 14 of the engine 10, as shown in FIG. 1.

The operation of the fuel vaporizing device 26 is preferably limited tothe lower load range, in particular to the idling range of the engine10. However it is also possible to provide the operation of the fuelvaporizing device 26 also in the partial load range that adjoins theidling range and even up to just before the full load of the engine isachieved. Particularly in the range of the upper partial load, afuel-air mixture can be produced in the lines 35, 38, 39, 41, 42, 43, 44which is too rich, i.e. has too high a percentage of fuel to achieveignition by means of spark plugs 19. An increase of the air percentageis not possible since the air quantity supplied to the mixing chamber 25is kept constant, for example, by a fixed throttle 32 provided in theidling line 24. However, this has no influence on the combustion in thecombustion chambers 13 of the cylinders 1 to 4, since after the deliveryof the excessively rich fuel-air mixture via the lines 41 to 44, anignitable fuel-air mixture is set once again by mixing with the airaspirated into the individual intake tubes 15. Upon introduction of thefuel-air mixture by means of the fuel vaporizing device 26, the fuelinjection valves 12 remain inactive, i.e. without injecting fuel. Onlythe central injection valve 27 of the fuel vaporizing device 26 deliversfuel in a fluid form, which then arrives in the electrically heatedvaporizer structure 29 in order to be heated in this and to at leastpartially vaporize. Due to the volume change of the liquid fuel thatoccurs with the heating, at the transition into the vaporous phase, thisis delivered into the mixing chamber 25. At the same time, air isbrought into the mixing chamber 25 via the idling air line 24 in orderto obtain an ignitable fuel-air mixture with λ=1 in the mixing chamber25 in the idling range, which is then delivered into the line system 36via the central line 35. The fuel percentage of the fuel-air mixture canbe controlled by means of the injection quantity of the centralinjection valve 27 of the fuel vaporizing device 26. The air quantitysupplied to the mixing chamber 25 should essentially correspond to theidling air quantity normally required in the idling operation of theengine. It is, however, also possible to provide an idle regulatingdevice 46, shown in FIG. 1 with dashed lines, on the idling air line 24in order to be able to control the air quantity supplied to the mixingchamber 25. After the end of the warm running phase or when there is aneed for more fuel, e.g. with sharp acceleration, when ascending amountain, or the like, in addition to or in lieu of mixture preparationby means of the fuel vaporizing device 26, a switch can be made over toconventional single injection with the fuel injection valves 12.

As explained above, in the line system 36 shown in FIG. 2, onlycylinders that are not operated with direct cylinder sequence or intakesequence are connected to each other and to the fuel vaporizing device26 so that for the cylinders 1, 2, 3, 4 that aspirate one after theother in the sequence 1-3-4-2, there are vapor line paths to the mixingchamber 25 with different lengths. Through a suitable length choice ofthe lines 38, 39, and 41 to 44, a reciprocal influence due to intaketube oscillations when the cylinders aspirate can be almost completelyprevented so that a uniform distribution of the fuel-air mixture formedin the mixing chamber 25 to the individual cylinders 1, 2, 3, and 4 ofthe engine 10 or combustion chambers 13 is produced.

FIG. 3 shows a second exemplary embodiment of the engine according tothe invention in which all of the same parts or parts which functionequivalently are given the same reference numerals as in FIGS. 1 and 2.FIG. 3 uses dashed lines to indicate an engine 10' that has sixcylinders 1, 2, 3, 4, 5, and 6, which, diverging from the depiction inFIG. 3, are in reality disposed one after the other in the sequence 1,2, 3, 4, 5, and 6 and are operated with an ignition sequence, forexample, of 1-5-3-6-2-4. The central line 35' leading away from the fuelvaporizing device 26 branches into a first cylinder pair line 48, asecond cylinder pair line 49, and a third cylinder pair line 50. Thefirst cylinder pair line 48 branches further into a first cylinder line51 for the first cylinder 1 and a second cylinder line 52 for the sixthcylinder 6. The second cylinder pair line 49 branches further into athird cylinder line 53 for the fifth cylinder 5 and a fourth cylinderline 54 for the second cylinder 2. The third cylinder pair line 50branches further into a fifth cylinder line 55 for the third cylinder 3and a sixth cylinder line 56 for the fourth cylinder 4. The resultingbranching points of the lines 48, 51, 52, and 49, 53, 54, and 50, 55, 56of the line system 36' have a Y-shape with legs, which preferablyenclose an angle that is as acute as possible between the branchinglines 51, 52; 53, 54; 55, 56. Since the first cylinder line 51 isconnected to the first cylinder 1, the second cylinder line 52 isconnected to the sixth cylinder 6, the third cylinder line 53 isconnected to the fifth cylinder 5, the fourth cylinder line 54 isconnected to the second cylinder 2, the fifth cylinder line 55 isconnected to the third cylinder 3, and the sixth cylinder line 54 isconnected to the fourth cylinder 4, the provided ignition sequence1-5-3-6-2-4 of cylinders 1 to 6 results in the fact that only respectivecombustion chambers or cylinders that are not operated in directignition sequence are connected to each other in pairs and are connectedto the fuel vaporizing device 26 via common lines 48, 49, 50 and via thecentral line 35'. As a result, for the cylinders 1 to 6 that aspirateone after the other in the sequence 1-5-3-6-2-4, there are in turn vaporline paths of different lengths to the mixing chamber 25 so that auniform distribution of the fuel-air mixture to the individualcombustion chambers 13 is possible without reciprocal influence of thecylinders 1 to 6.

The foregoing relates to preferred exemplary embodiments of theinvention, it being understood that other variants and embodimentsthereof are possible within the spirit and scope of the invention, thelatter being defined by the appended claims.

We claim:
 1. A multicylinder internal combustion engine having aplurality of cylinders each having a combustion chamber with externallysupplied ignition, which comprises an intake device from whichindividual intake tubes branch to each of the combustion chambers of theengine, at least one inlet valve per combustion chamber with a fuelinjection valve provided upstream of the inlet valve, said fuelinjection valve delivers fuel into the individual intake tube, and afuel vaporizing device that prepares a fuel-air mixture in particularoperating ranges of the engine, the fuel vaporizing device (26) isconnected via lines (38, 39, and 41 to 44; 48, 49, 50, and 51 to 56) tothe individual intake tubes (15) of the engine (10), and the lines (38,39, and 41 to 44; 48, 49, 50, and 51 to 56) branch downstream of thefuel vaporizing device (26) in such a way that only respectivecombustion chambers (13) that are not operated one after the other indirect ignition sequence are connected to each other in pairs viacylinder lines (41 to 44 or 51 to 56) and to the fuel vaporizing device(26).
 2. An engine according to claim 1, in which only combustionchambers (13) with the greatest chronological distance from each otherin the ignition sequence are connected to each other in pairs viacylinder lines.
 3. An engine according to claim 1, in which in an engine(10) with four cylinders (1, 2, 3, 4), two cylinder pair lines (38, 39)branch off from a central line (35) connected with the fuel vaporizingdevice (26), wherein each cylinder pair line (38; 39) branches furtherinto two cylinder lines (41, 42; 43, 44), which feed into individualintake tubes (15) of cylinders (1, 4; 2, 3) that are not operated in adirect ignition sequence (1-3-4-2).
 4. An engine according to claim 1,in which in an engine (10 ) with six cylinders (1, 2, 3, 4, 5, 6), threecylinder pair lines (48, 49, 50) branch off from a central line (35)connected with the fuel vaporizing device (26), wherein each cylinderpair line (48; 49; 50) branches further into two cylinder lines (51, 52;53, 54; 55, 56), which feed into individual intake tubes (15) ofcylinders (1, 6; 5, 2; 3, 4) that are not operated in a direct ignitionsequence (1-5-3-6-2-4).
 5. An engine according to claim 3, in which thecylinder lines (41 to 44; 51 to 56) feed into the individual intaketubes in the vicinity of the inlet valves (14).
 6. An engine accordingto claim 5, in which the branching points of the three lines (38, 41,42; 39, 43, 44; 48, 51, 52; 49, 53, 54; 50, 55, 56) have a Y-shape. 7.An engine according to claim 5, in which the branching points of thethree lines (38, 41, 42; 39, 43, 44; 48, 51, 52; 49, 53, 54; 50, 55, 56)enclose an angle that is as acute as possible between the lines (41, 42;43, 44; 51, 52; 53, 54; 55, 56).
 8. An engine according to claim 6, inwhich the branching points of the three lines (38, 41, 42; 39, 43, 44;48, 51, 52; 49, 53, 54; 50, 55, 56) enclose an angle that is as acute aspossible between the lines (41, 42; 43, 44; 51, 52; 53, 54; 55, 56). 9.An engine according to claim 4, in which the cylinder lines (41 to 44;51 to 56) feed into the individual intake tubes in the vicinity of theinlet valves (14).